Forum

[Tomshayes]

Hi again all.

Well now that I've opened a can of worms I am wondering where to go re bottom end.Top end will be 8.5:1 535 w 32mm AMAL 900 Concenttric.

I was going to retain standard gearing i.e 17 Tooth.

It seems to me there are a few options, I'm not a racer so prolonged flat out hi speeds aren't a real issue..


1) Retain existing standard Indian bottom end (Possibly with compression plate to lower comp a little)..
2) Improved ALLOY CONROD
2) Steel conrod retaining existing flywheels and Big End
3) Steel Conrod and Roller Bearing with original flywheels
4) Complete new 500 Crankshaft
5) New 570 crankshaft with Compression plate ..612cc The cost of option 4 and 5 being the same,,, If I fork out for new 500 crank then 670 would seem just as viable financially but what are the other advantages other than more cubes / torque

Any thoughts before I commit the wallet would be useful.

REgards

Tom

[Tomshayes]

Typo 570..

[Bullet Whisperer]

You could do what I put in my answer to your other thread, but also - lighten the flywheels - this makes a huge difference to acceleration, power, speed and even braking. The main bearings also get an easier life and you will NOT lose bottom end power, or torque, it is just a case of win, win, win, you will lose NOTHING!

[Tomshayes]

Great Paul

You've been a great help.

Well that's me told lol.

On the road for the spring.

Cheers again

Tom

[Valsp]

Its not all plain sailing. Lightened flywheels are useful in performance engines as the revs can increase and decrease more quickly. The momentum in the engine is maintained with a heavy flywheel. With a lightened flywheel the momentum is reduced and a hill has much more effect on the engine output. The engine also needs to be tuned to match the lightened flywheel. You don't want to go too light or your tick over may suffer. You will also need to have the flywheel properly balanced if you do reduce the weight

[Revband]

Option 6 is probably best, 6), trade it in for a bike that does what you want.

[Bullet Whisperer]

Valsp, a few pounds removed from a very heavy flywheel still leaves you with a heavy flywheel. The tickover and hill climbing abilities do not suffer, you will get up hills more quickly. As I mentioned elsewhere, I rebalance the flywheels after lightening them. There really is nothing to lose and everything to gain from doing this, but I don't care if no one wants to believe it.

[Tomshayes]

Hi Paul

I've seen you fly around Lydden so I'm with you mate lol.

What weight do you reduce the flywheels by?

Or what diameter do you decrease them to?

I assume you turn them down assembled on a lathe?

My mate Mark will probably be doing the bottom end work(You've met him BSA A65 Cafe Racer).

If not is this something that you could do?.. Mark is concerned that his press might not be man enough..

I'm not looking at putting it on the road before Spring March / April time.

I'm putting my 53 Meteor back together first. As Standard lol.. The Bullet is my Hack.. The Meteor is for sunny days and shows etc..

REgards

Tom

[Valsp]

Bullet whisperer you have far more knowledge of the Bullet than I do and I don't doubt you but the one thing I can't understand is why would any manufacturer waste money on using more material than necessary so why did Royal Enfield design the engine with such a heavy flywheel? As you say lightening the flywheel does reduce the demands on the bottom end so it does not make any sense to make it heavier than required

[Bullet Whisperer]

Valsp, I think the simple answer goes back to the days when the Bullet was a new design and sidecars were often bolted on to such machines. You would get a smoother standing start from your fully laden double adult Bullet outfit than you would if it had lighter flywheels. Incidentally, the Redditch 500 Bullets' cranks are about 3 or 4 lbs heavier than their Indian counterparts in standard form, but reducing an Indian crank assembly from about 22lbs to 19lbs still leaves you with something you would not want to drop on your foot and still a lot heavier than what you would probably find in an XBR 500, or similar. Also, a lot of people seem to confuse torque with flywheel effect and when you lighten the flywheels, you do not lose torque or bottom end power, but you will lose some flywheel effect, which is what gives a quicker standing start and acceleration etc. Regards, Paul.